Fine carbon fiber, method for producing the same and electrically conducting material comprising the fine carbon fiber

Abstract

A fine carbon fiber having an outer diameter of about 1 to about 80 nm and an aspect ratio of 10 to 30,000, comprising a hollow center portion and a multi-layer sheath structure of a plurality of carbon layers, the layers forming annual rings, wherein the sheath-forming carbon layers form an incomplete sheath, i.e., the carbon layers are partially broken or disrupted in a longitudinal direction, and the outer diameter of the carbon fiber and/or the diameter of the hollow center portion are not uniform in a longitudinal direction. The carbon fiber is obtained by instantaneously reacting a carrier gas at a high temperature and an organic compound gas kept at a temperature below the decomposition temperature of the transition metal compound and has a conductivity equivalent to that of a conventional vapor phase method and is useful as a filler material in resins, rubbers, paints and the like.

1 . A method for producing a fine carbon fiber, which comprises:
 vaporizing an organic compound solution containing an organic transition metal compound and, optionally a sulfur compound;   feeding the vaporized solution to a reaction furnace while the temperature of the solution is maintained below the decomposition temperatures of the organic transition metal compound;   feeding a carrier gas which has been heated to a high temperature to the reaction furnace through a path separate from that of the solution; and   combining the vaporized solution and the carrier gas in a heated reaction zone of about 700 to about 1,300° C. in the reaction furnace, to thereby carry out reaction instantaneously.   
     
     
         2 . The method for producing a fine carbon fiber as claimed in  claim 1 , wherein the temperature to which the carrier gas has been heated is about 500 to about 1,300° C. 
     
     
         3 . The method for producing a fine carbon fiber as claimed in  claim 1 , further comprising heat treatment. 
     
     
         4 . The method for producing a fine carbon fiber as claimed in  claim 3 , wherein the heat treatment temperature is about 900 to about 3,000° C. 
     
     
         5 . The method for producing a fine carbon fiber as claimed in  claim 3 , wherein the temperature to which the carrier gas has been heated is about 500 to about 1,300° C.